package com.algrithom.tree.avltree;

/**
 * 红黑树
 *
 * @param <K> 节点
 * @param <V> 节点
 * @author think
 * @version 1.0.0
 */
public class RBTree<K extends Comparable<K>,V> {
    
    // 静态布尔值变量、不可修改
    private static final boolean RED = true;
    
    private static final boolean BLACK = false;
    private Node root;
    private int size;
    
    public RBTree(){
        root = null;
        size = 0;
    }
    
    public int getSize(){
        return size;
    }
    
    public boolean isEmpty(){
        return size == 0;
    }
    
    // 判断节点node的颜色
    private boolean isRed(Node node){
        if (node == null) {
            return BLACK;
        }
        return node.color;
    }
    
    // 向红黑树中添加新的元素(key, value)
    public void add(K key,V value){
        root = add(root,key,value);
        root.color = BLACK; // 最终根节点为黑色节点
    }
    
    // 向以node为根的红黑树中插入元素(key, value)，递归算法
    // 返回插入新节点后红黑树的根
    private Node add(Node node,K key,V value){

        if (node == null) {
            size++;
            return new Node(key,value); // 默认插入红色节点
        }

        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left,key,value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right,key,value);
        } else { // key.compareTo(node.key) == 0
            node.value = value;
        }
        // 左旋转：右孩子是红色，左孩子是黑色
        if (isRed(node.right) && !isRed(node.left)) {
            node = leftRotate(node);
        }
        // 右旋转：左孩子是红节点，左孩子的左孩子是红节点
        if (isRed(node.left) && isRed(node.left.left)) {
            node = rightRotate(node);
        }
        // 颜色翻转：左右节点都是红色
        if (isRed(node.left) && isRed(node.right)) {
            flipColors(node);
        }
        return node;
    }
    
    // 返回以node为根节点的二分搜索树中，key所在的节点
    private Node getNode(Node node,K key){

        if (node == null) {
            return null;
        }
        if (key.equals(node.key)) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left,key);
        } else { // if(key.compareTo(node.key) > 0)
            return getNode(node.right,key);
        }
    }
    
    public boolean contains(K key){
        return getNode(root,key) != null;
    }
    
    public V get(K key){

        Node node = getNode(root,key);
        return node == null ? null : node.value;
    }
    
    public void set(K key,V newValue){
        Node node = getNode(root,key);
        if (node == null) {
            throw new IllegalArgumentException(key + " doesn't exist!");
        }
        node.value = newValue;
    }
    
    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node){
        if (node.left == null) {
            return node;
        }
        return minimum(node.left);
    }
    
    // 删除掉以node为根的二分搜索树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node){

        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }

        node.left = removeMin(node.left);
        return node;
    }
    
    // 从二分搜索树中删除键为key的节点
    public V remove(K key){

        Node node = getNode(root,key);
        if (node != null) {
            root = remove(root,key);
            return node.value;
        }
        return null;
    }
    
    private Node remove(Node node,K key){

        if (node == null) {
            return null;
        }
        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left,key);
            return node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right,key);
            return node;
        } else { // key.compareTo(node.key) == 0

            // 待删除节点左子树为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }

            // 待删除节点右子树为空的情况
            if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }

            // 待删除节点左右子树均不为空的情况

            // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置
            Node successor = minimum(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;

            node.left = node.right = null;

            return successor;
        }
    }
    
    //   node                     x
    //  /   \     左旋转         /  \
    // T1   x   --------->   node   T3
    //     / \              /   \
    //    T2 T3            T1   T2
    private Node leftRotate(Node node){

        Node x = node.right;

        // 左旋转
        node.right = x.left;
        x.left = node;

        x.color = node.color;
        node.color = RED;

        return x;
    }
    
    private Node rightRotate(Node node){

        Node x = node.left;

        // 左旋转
        node.left = x.right;
        x.right = node;

        x.color = node.color;
        node.color = BLACK;

        return x;
    }
    
    private Node flipColors(Node node){
        node.left.color = BLACK;
        node.right.color = BLACK;
        return node;
    }
    
    private class Node {

        public K key;

        public V value;

        public Node left, right;

        public boolean color;

        public Node(K key,V value){
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            // 默认新创建的的节点为红色
            color = RED;
        }
    }
}
